I definitely agree it is VERY poor taste to add on invites, but I don't think it is proper to invite a single-ton and not allow him or her to bring a guest. ...
There are so many different friends and family groups and "coupling" at weddings (who do you slow dance with if you are by yourself) and the bride and groom do so much hopping between guests, I think it is only right to allow everyone (married or not) to bring a guest so that they have an enjoyable evening too.

And to those who say that there are lots of people to socialize and dance with...reminds me of a divorced woman I worked with who told me about the previous year's Christmas party, where the women were whispering to and urging their SOs to go dance with her because she was all alone.

It was horrifiying and embarrassing. And before every says whatever in response, that kind of thing DOES happen...maybe not to you, and you'd never do it to anyone else...but if you're a singleton in a group of marrieds, it does happen sometimes. And I don't think anyone...bride/groom/DISers should be deciding that anyone shouldn't feel awkward in a situation because they themselves wouldn't.
I agree totally. While I find it rude to add guests to an RSVP, I find it equally, actually even more rude to invite single people without allowing for an escort to a wedding.
I would and did cut other areas of our wedding to make sure that each person was invited as a couple.

First thing we did when planning our wedding was make the guest list (including "and guests") and planned our reception accordingly.
BTW that phrase, "Flavor of the Week" bothers me. It seems to be used most often by those in a committed relationship. Don't you remember what it is like to date? I think it belittles the singles. I've been married a long time, and part of a couple for much longer, but I remember what it was like to be single and how once a person paired up we singles suddenly became third class citizens. I've tried, and hope that I have succeeded, to not do this to my friends.

"Flavor of the Week" is a really creepy phrase, IMHO.
if you open that door and invite some children, you are pretty much forced to invite all children. My kids have been excluded from a lot of weddings - love them a lot, but can bear to be apart from them for 4 hours or so, at an adult funtion.
Ditto.
I disagree with this. If you are a young couple with lots of friends that can be alot of people! DS and DFIL have a large circle of friends. If they have significant others, then they get invited...otherwise they will come single or decline. The only children being invited are my 2 and my 2 nieces. They are inviting 150, and if they included everyones kids and in significant others, I can't imagine what the guest amount would be.
The wedding couple get to decide who they want and the type of wedding they have. It is not rude of them to do this. As a guest if you don't like it, you don't have to go.
My cousins DD only had 2 kids, my brothers at her wedding. My youngest 2 were not invited. I made the decision not to attend. I know my family wasn't happy, but with my DH staying home with the kids, I knew I wouldn't have had a good time without him, so I made the decision.
It would be rude to invite a husband with out a wife and vice versa, or a person and not their fiance.
RSVPing or showing up with people not on the invite is beyond rude!!
Who determines what constitutes a "significant other"? How much time they spend together? (Two dates a week, 5?) If they live in the same state, or town and can see each other more often? Rank their love on some sort of "wedding planner" scale? Some people are ready to get married after 3 months of dating, some 5 years, so the amount of time together isn't necessarily a good indicator of "significant other" status.
My first date with my DH was 4th of July, 1979. By September, I knew "he's the one". We went to college together, I got an apartment down the street from his home (he worked for the landlady), we visited my parents together...we were definitely a couple, and very early on. The following September, I was invited to my cousin's wedding in NJ (I was in RI); my aunt, uncle and cousin had met (and very much liked) my DH. I grew up close to the bride (mom's sister's DD), and two other cousins who were also her cousins...one was a year older than me, one a year younger. Both of those cousins were married. So these two cousins who I grew up with almost as a "triplet" were, of course, invited with their spouses, and I wasn't invited with a guest. Yes, I thought it was rude and it was uncomfortable for me. I was 22 at the time...a big girl...I should've been invited with a guest. And might I add...I have now been married to my DH for 25 years; those two cousins have been divorced twice. (Just sayin'.) I would NEVER just have brought an uninvited guest, and I could have chosen not to go at all, but I did want to see my family and be a part of my cousin's wedding. That doesn't discount the rudeness factor of not being invited with a guest.
that it's rude to assume a guest will be invited, unless you are part of an established "social unit".
Again...what is an "established social unit". By whose standards? Married or engaged, and nothing else? Living together, and then eliminating those who choose not to live together? Dating for a certain number of years? What about dating for many years but choosing never to get married? Does that mean they never fit someone's definition of a social unit? Or should it be an age thing...if you're 19 and have been dating for two years, it's a "no guest", but if you're 30 and dating for a year, the guest is included?
I pulled my etiquette book from the 1940's and it says exactly the same thing. In fact if you thought the young lady might be part of a couple you would phone her mother and ask, if necessary you would obtain the young man's address and send the invite directly to him.
I'd have a problem with that, unless the young man would have been invited anyway, if the couple was no longer together. If the bride/groom expect that he'd be coming with "the young lady", I believe the invitation should go to her, for her to decide if she wants to bring him to the wedding. Perhaps she has a reason not to want him there...if he's part of a couple with her, it's up to her to decide. But, if he has since developed a strong relationship with the couple to be married and they specifically want him as a guest, then send a separate invitation. (Not based on "official" etiquette...JMHO.)
We went to a wedding last week, and boy, did DH and I have some issues with it. He didn't want to go for some reasons, and I insisted...this was his nephew getting married. But one thing that irked me...and yes, there are certainly bigger things in life...our invitation came addressed to "Mr John Smith and Family." I mean...did they look AT ALL in an etiquette book??? Might have well have said "Mr John Smith and whatsername and the kids."

(I cut out the address and have it on my refrigerator...it makes me laugh, as obnoxious as I think it is.) No inside envelope. Our kids didn't go (two are in college and had returned to school, so we didn't make DS go without them there); I was SO tempted to introduce myself in the receiving line (except there wasn't one, so we didn't even meet her family

except her mother who stopped by the table) as "and family."
I've been to weddings that my kids weren't invited to (have gotten a babysitter or left kids/DH at home), and wedding where they were and we took them. Both situations are fine with me.